This part is a kind of semiconductor called BCR405UW6.

Function of this product has 50 to 100mA LED CONSTANT CURRENT REGULATOR.

Manufacturers : Diodes

Image and pinout :

Some of the text within the PDF file :

BCR405UW6 50 to 100mA LED CONSTANT CURRENT REGULATOR in SOT26 Description The BCR405UW6 monolithically integrates a transistor, diodes and resistors to function as a Constant Current Regulator (CCR) for LED driving. The device regulates with a preset 50mA nominal that can be adjusted with external resistor up to 100mA. It is designed for driving LEDs in strings and will reduce current at increasing temperatures to self-protect. Operating as a series linear CCR for LED string current control then it can be used in applications with supply voltages up to 40V. With no need for additional external components, this CCR is fully integrated into a SOT26 minimizing PCB area and component count. Features  LED Constant Current Regulator Using PNP Emitter-Follower with Emitter Resistor to Curren [ ... ]

BCR405UW6 PDF Datasheet Download